Method for minimizing warp in the production of electronic assemblies

Abstract

The present invention relates to assembly techniques and the resulting products which are thermally stable, have high structural integrity, and compensate for thermal stresses that occur between the various components of the package. This is accomplished, in-part, by designing the package so that the coefficient of thermal expansion (CTE) of a stiffening ring which is mounted on the package substrate matches the CTE of the substrate and optional lid. Further, the particular adhesives used to bond the stiffening ring are chosen to match their CTE to that of the substrate, ring and lid. Moreover, the substrate is designed so that its CTE, at least in-part, matches that of the chip, and also that of the stiffening ring.

What is claimed is:  
     
       1. A method for minimizing warp in the production of electronic substrates, comprising the steps of: 
       arranging a plurality of dielectric and conductive layers symmetrically about a horizontal plane of symmetry;  
       selectively placing layers with the highest modulus and smallest thickness tolerance, relative to other layers, outwardly of the horizontal plane of symmetry; and  
       laminating the dielectric and conductive layers.  
     
     
       2. A method according to claim  1 , wherein the arranging step includes placing first and second dielectric layers respectively on opposite sides of a core layer, and first and second conductive layers respectively on opposite sides of the first and second dielectric layers. 
     
     
       3. A method according to claim  2 , wherein the first and second dielectric layers have approximately the same thickness and are made of the same material, the first and second conductive layers have approximately the same thickness and are made of the same material, and the first and second conductive layers have a higher modulus and smaller thickness tolerance than the first and second dielectric layers. 
     
     
       4. A method according to claim  3 , wherein the arranging step includes placing third and fourth dielectric layers respectively on opposite sides of the first and second conductive layer, and third and fourth conductive layers respectively on opposite sides of the second and third dielectric layers. 
     
     
       5. A method according to claim  4 , wherein the third and fourth dielectric layers have approximately the same thickness and are made of the same material, the third and fourth conductive layers have approximately the same thickness and are made of the same material, and the third and fourth conductive layers have a higher modulus and smaller thickness tolerance than the third and fourth dielectric layers. 
     
     
       6. A method according to claim  5 , wherein the third and fourth dielectric layers have a higher modulus than the first and second dielectric layers. 
     
     
       7. A method according to claim  5 , wherein the third and fourth conductive layers have a greater thickness than the first and second conductive layers. 
     
     
       8. A method of minimizing warp in the production of electronic packages, comprising the steps of: 
       forming a core layer;  
       arranging in a vertical stack about the core layer a plurality of alternatingly disposed dielectric and conductive layers, symmetrically about a plane of symmetry passing through the core layer and being arranged in a stack; and  
       selecting outer-most layers of the stack as conductive layers having substantially the same thickness, and the thickness of the outer-most conductive layers are thicker than any other conductive layers except for the core layer.  
     
     
       9. A method of minimizing warp in a multi-layered laminated structure having a plurality of pairs of opposing layers symmetrically disposed about a plane of symmetry, comprising the steps of: 
       offsetting an imbalance of bending moments that exists between one opposed pair of layers by purposely imbalancing a second opposed pair of layers, thereby creating an equal and opposite bending moment.